Let's dive into the details of what they have announced and provide some context.

First, the background. If you haven't already read it or just want to get a reminder on what heat restrictions are all about, read this post. As Rich points out in the video, the Framingham-Worcester line has the dubious distinction of being the most recent rail line brought under the complete control of the MBTA. The MBTA has invested quite a bit of money into construction projects to eliminate heat restrictions, and that work continues this spring.

Rich (and I) talk in railroad jargon about track 1 and track 2, and things like CP 4 and CP 11. Let's translate those into terms you can use to follow this story:

Track 1 = the northernmost track, or the track closest to New Hampshire. This is called the "outbound" track by Keolis customer service.Track 2 = the southernmost track, or the track closest to Rhode Island. This is called the "inbound" track by Keolis customer service. But note that between Boston and Framingham, rush hour trains use track 2 for BOTH the inbound and outbound legs of their journey. Hence why I hate calling the tracks "inbound" and "outbound."More about track numbering here.

CP = "Controlled Point." You can read about the definition of CP in the glossary.CP 4 = The interlocking just west of the new Boston Landing construction. CP 4 is where the two tracks from Worcester become a single track through the Beacon Park freight yard.CP 11 = What I call the "Weston switch," this is the interlocking between the Wellesley Farms and Auburndale stations, right next to the Leo J. Martin golf course and just west of Route 128.

The last time I posted an update about the rail destressing projects was in September of last year. At that time, the MBTA had either completed or planned for work on most of the tracks, but not all. Back then, I got the scoop on an expansion of the scope of the project. With that expanded scope, all of the rail was due to be destressed (or replaced) with the exception of track 2 from Worcester to Framingham.

With today's announcement from Keoils, that section - track 2 from Framingham to Worcester - is now scheduled to be destressed. So when these construction projects are complete, all the rail on both tracks will have been destressed, and heat restrictions will no longer be imposed on inbound OR outbound trains.

Track 2:CP 4 to Framingham - destressed in 2015Framingham to Worcester - will be destressed this spring.

You can use this map from last year to visually see what is happening. On that map, the dashed pink / orange line indicates track 2 where the rail destressing had not been scheduled (and hadn't even been funded until recently). Now, with today's news, that section of track will be destressed.

As you probably know, the heat restrictions usually only have a big impact on outbound rush hour trains. Outbound rush hour trains usually use track 2 from Boston to Framingham and then track 1 from Framingham to Worcester. As Rich mentions in the video, and as you can see from the list above, those tracks have already had destressing completed. So even without today's announcement, the prior work that has been completed will mean that heat restrictions this coming summer will have much less of an impact on the majority of daily Boston commuters.

But having heat restrictions on the other tracks can delay other trains, primarily because equipment that is delayed arriving in Boston can't leave ("turn") on time. So if an inbound afternoon rush hour train is delayed due to a heat restriction, an outbound train may be delayed even if it doesn't have a heat restriction on the path it is scheduled to follow. This is much more likely to happen now that they plan on keeping all equipment dedicated to a particular line with the implementation of the new schedules in May.

Other important tidbits from the video:

1) 30,000 ties to be replaced.2) a new interlocking at CP 6 will be created and constructed.3) a second track along the single track through the Beacon Park freight yard will be constructed, eliminating that single track bottleneck.

Although Rich doesn't state it in the video, I've been told that the second track through Beacon Park is part of this spring's construction project! That tidbit is probably the biggest news of the day. And buried here at the bottom so only you nerds that read this whole post will find out.

Until the new schedule is implemented (and/or the remaining heat destressing is 100% complete), we may still have heat related delays. For instance, the P528/P583 meet won't work if 528 is late due to heat restrictions west of Framingham. We also might still have problems (pre new schedule) with turns in South Station due to late inbound afternoon trains. It would be interesting to look at whether the new schedule (if it ever gets published) has any dependence on all the destressing work being done to make the schedule impervious to heat delays. But great (and BIG) news today for sure!

Reply

ChugChug

3/24/2016 00:23:57

Since the occasional heat wave over the life of the track is totally predictable, why not put in a handful of expansion joints? IDK how they'd need to be spaced, but even one expansion joint per half mile or so would eliminate heat kinks. The preheat temp could be set higher, because the rail shrink over that length wouldn't be enough to break the rail.

True, MBTA will never do anything 100% right, that's a mortal sin within that agency. But perhaps if it's written into their manual it could slip by them ;-)

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Dave

3/27/2016 21:38:45

The effect of heat on continuously welded rail has been researched in depth since the 1980's, and there have been many highly technical scholarly papers written on the topic. I've benefited from reading a number of them and I've been able to correspond with a few experts on the topic in order to understand more about it. I'm by no means an expert, but I can share what I've learned.

The solution of a handful of expansion joints isn't feasible because the rail has to be secured at very short intervals (actually every tie) in order to resist the forces imparted on it by trains. These lateral forces are huge on curves even where rails are superelevated. For expansion joints to work the rail would have to be 'loose' enough for the rail to expand towards and into the expansion joint. That 'looseness' could not be implemented in rail that needs to be restrained against the forces of high speed trains. Even on tangent (straight) track, rail needs to be restrained enough such that expansion joints wouldn't work.

The practice of destressing rails by raising their rail neutral temperature (RNT) effectively allows them to have a 'built-in' expansion joint within them. By restraining the rail at an elevated temperature, the rail is in constant tension when the temperature of the rail is below that installed temperature. Therefore, when it gets hot out, the expansion imparted by the 'heat wave' simply reduces the tension in the rail without elongating it. So the restrained tension of a rail installed at a high RNT acts as pre-installed continuous expansion joint, ready to soak up the expansion imparted by higher ambient and higher rail temperatures.

This comment and response are really more related to the first post about rail destressing. Read that for more on the topic, including some citations:
http://dbperry.weebly.com/blog/whats-with-the-heat-restrictions

Reply

Matt Ronn

3/29/2016 15:05:13

Does that mean a double track all the way to Yawkey?

Reply

Dave

3/29/2016 16:49:05

Yes.

To be precise, the current single track exists between CP 3 and CP 4. CP 3 is under the Commonwealth Ave. bridge, just west of Yawkey station. CP 4 is just west of the construction associated with the new Boston Landing station.

But yes, this construction project will eliminate the entire section of single track and replace it with a double track.

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As of late October 2017, the author is an MBTA employee. Blog posts prior to that time were created when I was NOT affiliated with the MBTA nor Keolis and therefore were my own opinion. Blog posts after October 2017 are my own personal statements and do not represent any official position or opinion of the MBTA and should not be construed as having been endorsed by the MBTA.